PROJECT SUMMARY Drug-Loaded Nanobubbles for Ultrasound Enhanced Delivery to Colon Cancer Liver Metastasis Most advanced cancers can spread to the liver including those of the breast, esophagus, stomach, pancreas, colon, lungs, kidneys and even melanoma. Liver metastases (also referred to as secondary liver cancer) cannot be cured in the majority of cases, and most patients presenting with liver metastases will die of the disease. The problem is most pronounced in colorectal cancer, where nearly 85% of the 150,000 patients diagnosed in the United States each year will eventually develop metastatic disease in the liver due to the shared blood supply between the intestine and the liver. Effective treatment options at this stage are severely limited, and most cases are treated with oral or intravenous chemotherapy. The median survival for patients receiving systemic chemotherapy is still only 21 months due primarily to low drug uptake in the tumor, serious systemic toxicity and heterogeneous drug distribution at tumor sites. To meet the urgent need for more effective treatment options for liver metastases, we plan to develop a hybrid theranostic nanobubble which is inherently ultrasound visible and ultrasound-deployable on demand in real time at the region of interest. Our exciting preliminary data demonstrate that even after a single application of ultrasound immediately following particle injection, ultrasound-triggered delivery leads to significantly higher drug concentration in tumors and results in more homogeneous distribution within tumor compared to free drug and non-triggered particles. This suggests that, especially after parameters are optimized, treatment of tumors with the proposed construct has the potential to maximize drug dose at the tumor site and should lead to improved survival. Within the scope of this project we thus propose to optimize formulation and treatment parameters essential to the success of this approach. Some aspects that distinguish our technology from others include 1) nanoparticles used in the study are 100-300 nm in diameter and yet have strong ultrasound response making them visible at clinically relevant frequencies of 3- 12 MHz; 2) nanoparticles have augmented cargo capacity to enable simple and efficient drug loading directly into the particle; 3) payload release can be triggered with the imaging transducer using standard pulse sequences already available on clinical scanners; 4) nanoparticle is self-assembled and thus easily formulated and scaled up. The project will be carried out in four aims with Aims 1 and 2 being dedicated to in vitro characterization and optimization of the construct and Aims 3 and 4 evaluating in vivo performance. The ultimate goal of this work is to develop and optimize an image-guided drug delivery strategy that will maximize drug accumulation in tumors and lead to augmented, homogeneous drug distribution within the tumor volume while minimizing systemic accumulation compared to free drug. The outcome of this research will be a more effective strategy to improve delivery of chemotherapeutic agents to metastatic liver tumors. Impact: We are confident that the advantages and unique aspects of our nanoparticles will enable successful completion of this objective. These nanoparticles will overcome the drug transport challenges and will improve the effectiveness of chemotherapy regimens used in treating secondary liver cancer with ultimate goal to translate this research to the clinic.